The present invention relates generally to optical touch sensor, and, more particularly, to an optical touch sensor having emitters and light detectors located on the same side.
Optical touch sensor employs light to detect the presence of one or more objects over a surface area. A conventional optical touch sensor employs an array of infrared (IR) light emitters located on one side of the surface area, and an array of IR light detectors located on an opposite side of the surface area. The array of IR light emitters is sequentially turned on one at a time to emit invisible IR light, which can be detected by at least one of the array of IR light detectors located directly opposite to the turned on light emitter if the light path is not blocked, otherwise there must be an object, such as a finger, placed on the surface blocking the light path. Therefore, the presence of the object on the surface and location thereof can be detected. Conventionally, to detect both x and y coordinates of an object, two sets of such light emitter and detector arrays must be deployed, one for each coordinate. Thus, all four sides of the surface area are surrounded by either the light emitters or the light detectors. Such conventional optical touch sensor apparently presents a significant structural limitation for its application.
As such, what is desired is an IR touch sensor that can be deployed only on one side of a surface area intended for touch sensing.